Graphics Reference
In-Depth Information
Figure 3-14. Left: bar graph with narrow grouped bars; right: with space between the bars
The first graph used
position="dodge"
, and the second graph used
position=posi-
tion_dodge()
. This is because
position="dodge"
is simply shorthand for
position=posi-
tion_dodge()
with the default value of 0.9, but when we want to set a specific value, we need
to use the more verbose command.
Discussion
The default value of
width
is 0.9, and the default value used for
position_dodge()
is the
same. To be more precise, the value of
width
in
position_dodge()
is the same as
width
in
geom_bar()
.
All of these will have the same result:
geom_bar(position
=
"dodge"
)
geom_bar(width
=
0.9
, position
=
position_dodge())
geom_bar(position
=
position_dodge(
0.9
))
geom_bar(width
=
0.9
, position
=
position_dodge(width
=
0.9
))
The items on the x-axis have
x
values of 1, 2, 3, and so on, though you typically don't refer to
them by these numerical values. When you use
geom_bar(width=0.9)
, it makes each group
take up a total width of 0.9 on the x-axis. When you use
position_dodge(width=0.9)
, it
spaces the bars so that the middleof each bar is right where it would be if the bar width were
0.9 and the bars were touching. This is illustrated in
Figure 3-15
. The two graphs both have the
same dodge width of 0.9, but while the top has a bar width of 0.9, the bottom has a bar width of
0.2. Despite the different bar widths, the middles of the bars stay aligned.
